using System.Diagnostics;
using System.Drawing.Imaging;
using System.Reflection;
using System.Reflection.PortableExecutable;
using System.Runtime.InteropServices;
using System.Threading.Tasks;
using System.Windows.Forms;
using Core;

namespace Desktop
{
    public partial class ParsonsForm1 : Form
    {
        private SmsMachine _machine = null!;
        private DebuggerForm _debugger;
        private Bitmap _screenBitmap = new Bitmap(256, 192, PixelFormat.Format32bppArgb);
        private Task _emulatorTask;
        private double TargetFrameTime = 16.667f;
        public int TotalFrameCount = 0;
        public double FrameTime { get; private set; } = 0;
        public double FramesPerSecond { get; private set; } = 0;
        private string _currentRomName = "No ROM";
        private Stopwatch _stopwatch = new System.Diagnostics.Stopwatch();
        public bool IsRunning { get; private set; } = false;

        public ushort? Breakpoint
        {
            get => _machine?.Breakpoint;
            set { if (_machine != null) _machine.Breakpoint = value; }
        }

        public ParsonsForm1()
        {
            InitializeComponent();
            this.Text = $"Parsons Master System 2026 - {_currentRomName}";
            _machine = new SmsMachine();

            PopulateIncludedRomsMenu();

            this.KeyPreview = true;
            this.KeyDown += Form1_KeyDown;
            this.KeyUp += Form1_KeyUp;
        }

        private void DrawScreen()
        {
            // Rapidly copy our VDP FrameBuffer into the Windows Bitmap
            var data = _screenBitmap.LockBits(new Rectangle(0, 0, 256, 192), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
            Marshal.Copy(_machine.VideoProcessor.FrameBuffer, 0, data.Scan0, _machine.VideoProcessor.FrameBuffer.Length);
            _screenBitmap.UnlockBits(data);

            // Update the PictureBox
            pbScreen.Image = _screenBitmap;
            TotalFrameCount++;
        }

        public void StartEmulator()
        {
            if (IsRunning) return;
            IsRunning = true;
            TotalFrameCount = 0;

            double TargetFrameTime = 1000.0 / 60.0;

            _emulatorTask = Task.Run(() =>
            {
                _stopwatch.Restart();

                double nextFrameTargetTime = _stopwatch.Elapsed.TotalMilliseconds + TargetFrameTime;
                double lastFpsUpdate = _stopwatch.Elapsed.TotalMilliseconds;
                int framesThisSecond = 0;

                while (IsRunning)
                {
                    // Mark exactly when the emulator starts thinking
                    double frameStartTime = _stopwatch.Elapsed.TotalMilliseconds;

                    // 1. Do the heavy lifting (Z80 and VDP)
                    _machine.RunFrame();

                    // 2. FIRE AND FORGET! Tell Windows to draw, but DO NOT WAIT for it to finish!
                    BeginInvoke((System.Windows.Forms.MethodInvoker)delegate { DrawScreen(); });

                    // 3. Safety catch
                    if (_machine.Breakpoint.HasValue && _machine.Cpu.PC == _machine.Breakpoint.Value)
                    {
                        IsRunning = false;
                        BeginInvoke((System.Windows.Forms.MethodInvoker)delegate { _debugger?.uiUpdateTimer_Tick(null, EventArgs.Empty); });
                        break;
                    }

                    // 4. Calculate TRUE Frame Time (Compute Time) BEFORE we go to sleep!
                    FrameTime = _stopwatch.Elapsed.TotalMilliseconds - frameStartTime;

                    // --- HIGH PRECISION THROTTLE ---
                    while (_stopwatch.Elapsed.TotalMilliseconds < nextFrameTargetTime)
                    {
                        if (nextFrameTargetTime - _stopwatch.Elapsed.TotalMilliseconds > 2.0)
                        {
                            Thread.Sleep(1);
                        }
                        else
                        {
                            Thread.SpinWait(10);
                        }
                    }

                    // --- METRICS MATH ---
                    double currentTime = _stopwatch.Elapsed.TotalMilliseconds;
                    TotalFrameCount++;
                    framesThisSecond++;

                    if (currentTime - lastFpsUpdate >= 1000.0)
                    {
                        FramesPerSecond = framesThisSecond / ((currentTime - lastFpsUpdate) / 1000.0);
                        framesThisSecond = 0;
                        lastFpsUpdate = currentTime;

                        BeginInvoke((System.Windows.Forms.MethodInvoker)delegate {
                            this.Text = $"Parsons Master System - {_currentRomName} [FPS/FT: {FramesPerSecond:F0}/{FrameTime:F1}]";
                        });
                    }

                    nextFrameTargetTime += TargetFrameTime;

                    if (currentTime > nextFrameTargetTime + TargetFrameTime)
                    {
                        nextFrameTargetTime = currentTime + TargetFrameTime;
                    }
                }
            });
        }

        public void StopEmulator()
        {
            IsRunning = false;
        }


        public void StepEmulator()
        {
            _machine.StepMachine();
        }

        private async void LoadRomAndStart(string filePath)
        {
            StopEmulator();
            if (_emulatorTask != null)
            {
                await _emulatorTask;
            }

            // 2. Load the file
            byte[] rom = File.ReadAllBytes(filePath);

            // 3. Jam it into the Sega Mapper
            _machine.LoadCartridge(rom);

            _currentRomName = Path.GetFileNameWithoutExtension(filePath);
            this.Text = $"Parsons Master System - {_currentRomName}";

            // 5. Turn the power on!

            StartEmulator();
        }

        private void PopulateIncludedRomsMenu()
        {
            // The folder you used for Golden Axe Warrior
            string romsDirectory = @"C:\Parsons\Local Code Projects\ParsonsMasterSystem2026\Desktop\ROMS\";

            if (Directory.Exists(romsDirectory))
            {
                string[] romFiles = Directory.GetFiles(romsDirectory, "*.sms");

                foreach (string file in romFiles)
                {
                    // Create a new dropdown item for each .sms file it finds
                    string romName = Path.GetFileNameWithoutExtension(file);
                    ToolStripMenuItem romMenuItem = new ToolStripMenuItem(romName);

                    // When clicked, pass the file path to our helper method
                    romMenuItem.Click += (sender, e) => LoadRomAndStart(file);

                    // Add it to the "Included" submenu (make sure the name matches your designer element!)
                    includedToolStripMenuItem.DropDownItems.Add(romMenuItem);
                }
            }
        }

        private void selectROMToolStripMenuItem_Click(object sender, EventArgs e)
        {
            using (OpenFileDialog ofd = new OpenFileDialog())
            {
                ofd.Title = "Select Master System ROM";
                ofd.Filter = "SMS ROMs (*.sms)|*.sms|All Files (*.*)|*.*";

                if (ofd.ShowDialog() == DialogResult.OK)
                {
                    LoadRomAndStart(ofd.FileName);
                    _machine.Reset();
                }
            }
        }

        private void resetToolStripMenuItem_Click(object sender, EventArgs e)
        {
            _machine.Reset();
        }

        private void debuggerToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (_debugger == null || _debugger.IsDisposed)
            {
                _debugger = new DebuggerForm(_machine.Cpu, _machine.MemoryBus, this);
            }
            _debugger.Show();
        }

        private void includedToolStripMenuItem_Click(object sender, EventArgs e)
        {

        }

        private void exitToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Environment.Exit(0);
        }

        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
            UpdateJoypad(e.KeyCode, true);
        }

        private void Form1_KeyUp(object sender, KeyEventArgs e)
        {
            UpdateJoypad(e.KeyCode, false);
        }

        private void UpdateJoypad(Keys key, bool isPressed)
        {
            if (_machine == null) return;

            byte bitMask = 0;

            // Map your keys to the Sega hardware bits
            switch (key)
            {
                case Keys.W: bitMask = 0x01; break; // Bit 0: Up
                case Keys.S: bitMask = 0x02; break; // Bit 1: Down
                case Keys.A: bitMask = 0x04; break; // Bit 2: Left
                case Keys.D: bitMask = 0x08; break; // Bit 3: Right
                case Keys.O: bitMask = 0x10; break; // Bit 4: Button 1 (Start/Action)
                case Keys.P: bitMask = 0x20; break; // Bit 5: Button 2
                default: return; // Ignore any other keys
            }

            if (isPressed)
            {
                // Active-Low: Clear the specific bit to 0 using a bitwise AND with a NOT mask
                _machine.IoBus.Joypad1State &= (byte)~bitMask;
            }
            else
            {
                // Active-Low: Reset the specific bit to 1 using a bitwise OR mask
                _machine.IoBus.Joypad1State |= bitMask;
            }
        }
    }
}